Movement correcting apparatus with shiftable image read-out area

ABSTRACT

An image pick-up device capable of moving a detection region set on a picked-up picture by following the movement of an object image, wherein it is constructed to control a setting position of said detection region by detecting an object position on the picked-up picture, and further to control the moving range, response speed and size of said detection region, depending on the depth of field.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/859,567,filed May 20, 1997, now U.S. Pat. No. 5,739,857, which is a continuationof application Ser. No. 08/158,187, filed Nov. 24, 1993, now abandoned,which is a continuation of application Ser. No. 07/650,758, filed Feb.5, 1991, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automatic focusing deviceappropriate for use in a pick-up device, such as a video camera, aelectronic still camera or the like.

2. Related Background Art

Conventionally, an image pick-up device such as a video camera isprovided with a known method for focusing in which the focusing lensposition is controlled by detecting the definition of an object imagefrom the high-frequency component of a video signal which is output frompick-up means such as a CCD or the like, and making it maximum.

Further, in a camera converting an optical object image into an electricsignal with such pick-up means, a method for the automatic focusing isproposed in which part of a picked-up picture is used as a focusingdetection region, which is forced to follow the movement of the objectto adjust into the focusing state automatically (e.g. Japanese Laid-OpenPatent Application No. 60-249477.)

According to this conventional method, a move position of the object isobtained by sensing a characteristic point of the object within thefocusing detection region and detecting the change thereof, and then thefocusing detection region is reset on a small region centered on themove position.

However, since such a conventional pick-up device performs the trackingof an object with a focusing detection region of the same size and atthe same response speed for every field in any of the pick-up situation,there occurs a problem that the focusing detection region may moveunstably irrespectively of the object, for example, when the depth offield is large, in which it is difficult to distinguish a main objectfrom the environment, i.e., background, in tracking the object toextract a peak of the high-frequency component of such object image(so-called a far and near contention).

SUMMARY OF THE INVENTION

It is a first objective of the present invention to resolve theabove-mentioned problem by enabling the automatic object trackingadapted for a pick-up situation.

A second objective of the present invention is to provide an automaticobject tracking device capable of tracking a moving object stably andreliably, whatever a pick-up situation may be.

A third objective of the present invention is to provide an automaticobject tracking device capable of tracking a moving object precisely bycontrolling a moving range, response speed, moving direction, and sizeof the detection region, depending on the depth of field.

To accomplish these objectives, in accordance with a preferredembodiment of this invention, an image pick-up device capable of movinga detection region set on a picked-up picture by following the movementof an object image is disclosed, wherein the device comprises, positiondetection means for detecting an object position on said picked-uppicture, region setting means for controlling a setting position of saiddetection region based on the output of said position detection means,and restriction means for restricting a moving range of said detectionregion according to a predetermined information of a pick-up state.

A fourth objective of the present invention is to provide an automaticfocusing device capable of continuing to focus on a moving object,irrespective of the pick-up condition.

A fifth objective of the present invention is to provide an automaticfocusing device capable of following an object image of interest, bymaking the movement of focusing detection region natural even when thedepth of field is large.

To accomplish these objectives, in accordance with a preferredembodiment of this invention, an image pick-up device capable of movinga detection region set on a picked-up picture by following the movementof an object image is disclosed, wherein the device comprises positiondetection means for detecting an object position on said picked-uppicture, region setting means for controlling a setting position of saiddetection region based on the output of said position detection means,and restriction means for restricting a moving range of said detectionregion according to an information of the depth of field.

A sixth objective of the present invention is to optimize the responsecharacteristic to the tracking of an object, according to a pick-upcondition.

To accomplish these objectives, in accordance with a preferredembodiment of this invention, an image pick-up device capable of movinga detection region set on a picked-up picture by following the movementof an object image is disclosed, wherein the device comprises positiondetection means for detecting an object position on said picked-uppicture, region setting means for controlling a setting position of saiddetection region based on the output of said position detection means,and control means for controlling a response speed to the movement ofsaid detection region according to an information of the depth of field.

A seventh objective of this invention is to provide a pick-up devicecapable of continuing to focus on a moving object, irrespective of thechange of the depth of field.

To accomplish such an objective, in accordance with a preferredembodiment of this invention, an image pick-up device capable of movinga detection region set on a picked-up picture by following the movementof an object image is disclosed, wherein the device comprises positiondetection means for detecting an object position on said picked-uppicture, region setting means for controlling a setting position of saiddetection region based on the output of said position detection means,and control means for controlling a moving direction, movement responsespeed, and size of said detection region according to an information ofthe depth of field.

An eighth objective of this invention is to provide an image pick-updevice capable of performing a stable and reliable focusing operationfor tracking an object, which permits the optimized control of a size,movement response speed, and moving direction of the focusing detectionregion at any time, irrespective of a pick-up condition, to enable theobject to be positioned within the focusing detection region at alltimes.

A ninth objective of the present invention is to provide a pick-updevice capable of continuing to focus on a moving object reliably, inwhich a main object is caught within a focusing detection region at anytime, irrespective of the depth of field, with a stable and precisetracking of the object without malfunction such as a far and nearcontention, by switching and controlling appropriately the size, movingdirection and response speed of the focusing detection region within apicked-up picture, depending on the depth of field.

A tenth object of the present invention is to provide a pick-up devicewith the automatic focusing adjustment having a mode of continuing tofocus on a moving object while tracking the object, in which an operatorcan distinctly recognize a current mode of the focusing adjustmentoperation.

An eleventh object of the present invention is to provide a pick-updevice capable of distinctly displaying on a monitor screen whether thecurrent focusing detection mode is due to a fixed focusing detectionregion or a moving focusing detection region following the movement ofan object, so that an operator can recognize a current focusingadjustment mode correctly, and various malfunctions and misoperationsare prevented.

A twelfth objective of the present invention is to provide a focusingdetection device capable of performing a stable and precise tracking ofan object, by setting a first focusing detection mode in which thefocusing operation is performed with the focusing detection region fixedat a predetermined position on a picked-up picture or a second focusingdetection mode in which the focusing operation is performed with saiddetection region tracking the object, and in which said focusingdetection region is displayed within a monitor screen, and further thecurrent focusing detection mode, i.e., the on/off status of an automaticobject tracking operation, is distinctly displayed within the monitorscreen, as said first and second focusing detection modes have differentdisplays for the focusing detection region, so that an operator canrecognize a current pick-up condition correctly, and variousmalfunctions and misoperations can be prevented.

To accomplish these objectives, in accordance with a preferredembodiment of the present invention, an automatic focusing device isdisclosed, in which the device comprises region setting means forsetting a focusing detection region on a picked-up picture, objecttracking means for controlling said region setting means by detectingthe movement of an object image and moving a setting position of saidfocusing detection region by following said object image, focus controlmeans for enabling the setting of a first focusing detection mode inwhich the focusing operation is performed with said focusing detectionregion fixed at a predetermined position on said picked-up picture, or asecond focusing detection mode in which the focusing operation isperformed with said detection region tracking the object, and displaymeans for displaying said first focusing detection mode and said secondfocusing detection mode differently, as well as displaying said focusingdetection region within a monitor screen.

A thirteenth objective of the present invention is to provide a pick-updevice capable of distinctly displaying on a monitor screen such as anelectronic view finder whether or not the current object trackingoperation is performing a normal tracking of an object of interest,whereby an operator can recognize precisely the tracking operationcondition in the current object tracking mode, and so variousmalfunctions and misoperations can be prevented.

Another objective of the present invention is to provide an automaticfocusing device with the automatic object tracking feature enabling astable and precise object tracking, which can continue to focus on amoving object by following the object, wherein the device can distinctlydisplay on a monitor screen a state where the object tracking isnormally performed to continue to focus on the moving object or a statewhere the object tracking is not normally performed so that the movingobject is not focused on, because it is configured to display whether ornot the object tracking operation is normally performed, with a decisionfrom a condition of the focusing control system, whereby an operator canrecognize precisely a current pick-up condition and various malfunctionsand misoperations can be prevented.

To accomplish these objectives, in accordance with a preferredembodiment of the prevent invention, an automatic focusing device isdisclosed, wherein the device comprises region setting means for settinga predetermined detection region on a picked-up picture, focusingdetection means for detecting the focusing on an object image withinsaid detection region, object tracking means for controlling said regionsetting means by detecting the movement of said object image and movinga setting position on said focusing detection region by following saidobject image, decision means for deciding an operation state of saidobject tracking means based on the output of said focusing detectionmeans, and display means for displaying the operation state of saidobject tracking means based on a decision result from said decisionmeans.

Other objectives and features of the present invention will becomeapparent from the following detailed description, in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of a pick-up deviceaccording to the present invention.

FIG. 2 is a flowchart for explaining the control operation of thepick-up device according to the present invention.

FIG. 3 is a view showing an operation table for the depth of field onthe pick-up device according to the present invention.

FIGS. 4A to 4C are views showing the positional relations of a focusingdetection region within a picked-up picture on the pick-up deviceaccording to the present invention.

FIGS. 5A to 5C are views for explaining another example of the controlof a focusing detection region within a picked-up picture on the pick-updevice according to the present invention.

FIG. 6 is a flowchart showing another example of the control operationof the pick-up device according to the present invention.

FIG. 7 is a view for explaining the display corresponding to a focusingstate on the object tracking mode according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An automatic focusing device according to one embodiment of the presentinvention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an automatic focusing device of thisinvention applied to a video camera or the like.

In this figure, 1 indicates a pick-up lens system having a focusing lens1A for adjusting a focus and a zoom lens 1B for performing the zoomoperation. The focusing lens 1A is driven and controlled by means of afocusing motor driving circuit 9 and a focusing motor 10, while the zoomlens 1B is driven and controlled by means of a zoom motor drivingcircuit 11 and a zoom motor 12. 2 is an iris for controlling the amountof incident light, in which it is driven and controlled by means of aniris driving circuit 7 and an ig meter 8 for driving iris. 3 is apick-up element such as CCD for photoelectrically converting an objectimage formed on a picked-up picture with the focusing lens 1 into apick-up signal, 4 is a preamplifier for amplifying the pick-up signalthat is output from the pick-up element 3 to a predetermined level, and5 is a process circuit for converting an image signal that is outputfrom the preamplifier 4 into a normalized standard television signal,with predetermined processings such as gamma correction, blankingprocessing and the addition of synchronizing signal, and outputting itfrom a video output terminal. The television signal output from theprocess circuit 5 is supplied to a monitor 23 such as a video recorderor electronic view finder not shown.

6 is an iris control circuit for automatically controlling the ig meter8 via the iris driving circuit 7 such that the image signal output bythe preamplifier 4 is input and the aperture size of the iris 2 isadjusted to maintain the level of said image signal constant at apredetermined level.

13 is a full-range filter set to be able to determine whether or notthere is an object by determining whether the contrast of object islarge or small from the image signal output by the preamplifier 4, 14 isa band-pass filter for extracting a high-frequency component necessaryto detect the focusing also from the image signal output by thepreamplifier 4, and 15 is an detection circuit for detecting anunfocused width (width between edge portions of object image) of objectimage from the image signal, in which it detects the focusing by usingsuch a property that the closer the focusing state, the smaller theunfocused width of object image is. As a focusing detection method assuch with the unfocused width detection circuit is known in JapaneseLaid-Open Patent Application No. 62-103616, the detail therefor isomitted.

16 is a gate circuit for passing only a signal which falls within aspecified region on the picked-up picture, by gating the output from theobject decision filter 13, the band-pass filter 14 and the unfocusedwidth detection circuit 15, in which only a portion of a video signal ofone field corresponding to that within a specified region is passed, inaccordance with a gate pulse supplied by a logic control circuit 18 aswill be described later, thereby enabling the setting of a passageregion for extracting the high-frequency component, i.e., a focusingdetection region for performing the focusing detection, at any positionwithin the picked-up picture (the focusing detection regions set on thepicked-up picture are shown in FIG. 4 and the detail of each figure willbe described later).

17 is a peak position detection circuit for detecting the horizontal andvertical positions within the picked-up picture where a peak value ofthe high-frequency component is obtained from the image signalcorresponding to that within the focusing detection region that wasextracted by the gate circuit 16. This peak position detection circuitoutputs the horizontal and vertical coordinates of the peak positiondetected during one field period, by dividing the focusing detectionregion into a predetermined number of blocks in the horizontal andvertical directions, and detecting in which block the peak positiondetected during one field period is located.

19 is a focus encoder for detecting a move position of the focusing lens1A, 20 is a zoom encoder for detecting an information of the focaldistance changeable with the zoom lens 1B, and 21 is an iris encoder fordetecting the amount of aperture for the iris 22. These detection dataare supplied to the logic control section 18.

18 is a logic control circuit for controlling the entire system totally,for example, constructed of a microcomputer, within which are providedan input/output port not shown, A/D converter, read only memory (ROM),and random access memory (RAM). This logic control circuit fetches thepeak value and its peak position coordinates of the high-frequencycomponent within one field period based on the output of the bandpassfilter 14 output from the peak position detection circuit 17, the objectcontrast information based on the output of the object decision filter13, the unfocused width information based on the output of the unfocusedwidth detection circuit 15 and the detection information from eachencoder, which were output from the peak position detection circuit 17,and operates them according to a predetermined algorithm, whereby fromtheir time series variations, the settings of a position, size, movingdirection and movement response speed of the focusing detection regionon a picked-up picture are performed, or the object tracking is carriedout, while the moving direction and moving speed of a focusing lens atwhich the focusing point is obtained are implemented.

That is, the movement of an object is detected for each field, from thepeak value and its peak position coordinates of the high-frequencycomponent within one field period based on the output of the bandpassfilter 14, a gate pulse is supplied to the gate circuit 16 for theon/off control to set the focusing detection region around a positioncentered on the changed peak position, i.e., object position, and only aportion of an image signal corresponding to that within the focusingdetection region is passed.

The logic control circuit 18 also performs the focusing detection forthe object, based on the image signal corresponding to that within thefocusing detection region that has been set, thereby adjusting thefocusing point. That is, it fetches unfocused width information suppliedfrom the unfocused width detection circuit 15 and peak value informationof the high-frequency component supplied from the bandpass filter 14,and supplies control signals, such as a rotational direction, rotationalspeed, start/stop of rotation for the focusing motor 10, to the focusdriving circuit 9, so that the focusing lens 1A should be driven to aposition where the unfocused width within one field is minimum and thepeak value of the high-frequency component is maximum, therebycontrolling the focus driving circuit 9.

In this case, the logic control circuit 18 controls the size, movingrange and movement response speed for the focusing detection region,according to the focusing degree, and the depth of field obtained froman iris value and a focal distance detected by the iris encoder 21 andthe zoom encoder 20, respectively.

In this way, it is possible to focus on a moving object while performingthe automatic tracking thereof.

Here, in the present invention, the use of an unfocused width signaloutput by the unfocused width detection circuit 15 and a peak value ofthe high-frequency component output by the bandpass filter 14 for thedetection of focusing is based on the following reason.

That is, while the unfocused width has such a characteristic that itprovides a high accuracy of the focusing detection near or at a focusingpoint due to the unsusceptibity to the effect of object contrast,because the unfocused width is smaller near the focusing point andminimum at the focusing point, it can not provide a sufficient accuracyof the focusing detection far off the focusing point, it has a narrowdynamic range.

On the contrary, while the high-frequency component can provide theoutput corresponding to the focusing degree even far away from thefocusing point, because the dynamic range is wide, it can not give assufficient accuracy for the focusing detection as that of the unfocusedwidth detection, as a whole, due to a large effect of the contrast.

Accordingly, a focusing detection method can be realized with acombination of them, in which the dynamic range is wide and a highdetection accuracy can be obtained near the focusing point.

The logic control circuit 18 also gets and detects regularly thecontrast within the focusing detection region within a picked-uppicture, based on the output of the object decision filter 13, therebydetermining whether there is an object within the picked-up picture ornot.

That is, if an object image is outside of the picked-up picture, or in acondition where the contrast between the object and the background canhardly be obtained due to an extremely unfocused state, the objectdecision becomes itself impossible, so that the object can not betracked precisely, and thus malfunctions are liable to occur and thefocal adjustment is performed incorrectly.

In view of the above-mentioned problems, according to this invention, itis determined from the contrast within a picked-up picture whether ornot there is an object, and if there is no object, the movement of thefocusing detection region, i.e., the object tracking operation, isstopped to avoid malfunctions owing to unnatural movement of thefocusing detection region and the false detection of other than anobject.

And, according to this invention, a configuration is taken such that bydetecting the depth of field in performing the above-mentioned automatictracking of object, the size, moving direction and response speed of thefocusing detection region are controlled, thereby enabling the optimalobject tracking operation.

A gate pulse output from the logic control circuit 18, after beingsubjected to a predetermined signal processing not only via the gatecircuit 16 but the display circuit 22, is superimposed onto a televisionsignal output by the process circuit 5, supplied to the monitor 23,where the focusing detection region is superimposed within a monitorscreen, and is displayed by lighting or blinking it, depending on thestate of focus adjustment.

Next, the control operation of the focusing detection region with anautomatic focusing device according to the present invention will bedescribed sequentially with reference to a flowchart shown in FIG. 2. Itshould be noted that the automatic object tracking operation of thisinvention can operate in the AF (automatic focusing adjustment) mode,but is made inoperative in the manual focusing adjustment mode, in whichthe focusing detection region is not displayed onto the monitor screen.

It should be also noted that there are provided in the presentinvention, the AF mode accompanying the object tracking operation andthe normal AF mode not accompanying the object tracking operation, inwhich the mode during operation can be distinguished with an indicationwithin the monitor screen.

In FIG. 2, the object tracking control flow is started, and then thesystem is initialized at step S1, in which the focusing detection regionis set at an initial position on almost central portion within apredetermined picked-up picture, and its size is set maximum.

Next, at step S2, a determination is made whether the automatic objecttracking mode is on or not.

If the tracking mode is off at step S2, the processing proceeds to stepS26, in which the setting for displaying by lighting the focusingdetection region within the monitor screen is performed while thefocusing detection region is left fixed at the initial position ofalmost central portion on the picked-up picture, and subsequently the AFoperation is performed in steps S27-S33. An algorithm of this AFoperation is the same as that of the AF operation as shown in stepsS5-S12 in the object tracking operation, and therefore it will bedescribed later.

After terminating the flow of the AF operation, the processing proceedsto step S34, in which the focusing detection region is displayed bylighting within the monitor screen according to the setting at step S26,and it returns to step S2. That is, in the normal AF mode notaccompanying the object tracking operation, the focusing detectionregion is displayed by lighting.

If it is determined that the tracking mode has been set at step S2, theprocessing proceeds to step S3, in which a determination is made whetherthe tracking operation has been started, or it is in a stand-by statebefore starting of the tracking operation. If the tracking operation isin the stand-by state, the processing proceeds to step S35, in which thesetting for displaying by blinking the focusing detection region withinthe monitor screen is performed to indicate the stand-by state oftracking, while the focusing detection region remains in the initialposition set at step S1. Thereafter the AF operation is carried out atstep S27-S33, and then the processing proceeds to step S34, in which thefocusing detection region is displayed by blinking within the monitorscreen according to the setting at step S26, and it returns to step S2.That is, in the stand-by mode of the object tracking operation, thefocusing detection region can be displayed by blinking it within themonitor screen.

If the tracking has been started at step S3, the processing proceeds tostep S4, in which the setting for displaying by blinking the focusingdetection region within the monitor screen is performed to show theautomatic object tracking mode for continuing to focus on a movingobject by automatically tracking it on the focusing detection regionwithin the picked-up picture. It should be noted that the display of theobject tracking mode can be distinguished from that of the trackingstand-by mode, for example, with different blinking periods.

Entering the automatic object tracking operation, at step S5, an irisvalue detected by the iris encoder 21 is fetched into the logic controlcircuit 18 for each field, converted into digital data of for exampleone byte with the A/D conversion circuit within the logic controlsection 18, and then read into the memory. At step S6, a digital signalof focal distance information detected by the zoom encoder 20 is fetchedinto the logic control section 18, and read into the memory for eachfield.

At step S7, the depth of field is obtained based on the iris value andthe focal distance fetched at steps S5 and S6, respectively. Thisoperation of the depth of field is performed with a decision table forthe depth of field, as shown in FIG. 3, which has been written into ROMwithin the logic control circuit 18. In an example of the informationtable as shown in FIG. 3, the depth of field is determined at one ofthree stages for the regions DP1, DP2 and DP3, depending on theinformation of the iris value F and the focal distance f. In the samefigure, the depth of field is deeper in the order of DP1, DP2 and DP3.

At step S8, based on the output from the peak position detection circuit17, the information of horizontal and vertical positions for a peakvalue of the high-frequency component of a brightness signal within onefield period, in a unit of block within the picked-up picture, is readinto the logic control circuit 18.

At step S9, the unfocused width information within that field that wasoutput from the unfocused width detection circuit 15, and at step S10,the peak value information within that field that was output from thebandpass filter 14 are read into the memory after the A/D conversionwithin the logic control circuit 18, respectively. And at step S11, thefocusing detection is performed from the information about the depth offield, unfocused width and peak value of the high-frequency component,in order to obtain and determine the drive speed which corresponds to adrive direction and a focusing degree of the focusing lens 1A. In thiscase, the speed of focusing lens is corrected in view of the depth offield obtained from the iris value and focal distance. In determiningthe depth of field and the drive speed, the operation time can beshortened and the program simplified, by making use of an informationtable as shown in FIG. 3 or an information table not shown for settingthe speed to determine it from the focusing degree and the depth offield, which is stored in ROM as previously described.

At step S12, the focusing lens drive information (focusing motor drivespeed, drive direction, control signal such as drive/stop) is suppliedto the focus motor driving circuit 9 to drive the focusing motor 10,thereby moving the focusing lens 1A to the focusing point.

At step S13, the analog contrast information within that field output bythe object decision filter 13 is transformed into a digital form withthe A/D conversion, which is read into a predetermined memory areawithin the logic control circuit 18, and at step S14, a predeterminedoperation is performed to decide the contrast of object. Morespecifically, by comparing the information of the level of a brightnesssignal output by the object decision filter 13 with a predeterminedthreshold, the contrast of object is determined, whereby it is decidedwhether the automatic tracking with a high precision based on thevariations of the peak value of the high-frequency component ispossible, or the object tracking is impossible due to a low brightness.

If it is determined at step S14 that the contrast of object issufficiently high so that the object reliably exists within the focusingdetection region, and the object tracking with a high precision ispossible, the processing proceeds to steps from S15 on, in which thesize, moving direction and response speed of the focusing detectionregion (also used as the object tracking region) are obtained based onthe information of the depth of field obtained at step S7.

That is, at step S15, the depth of field obtained at step S7 is decided,and if it is DP3 that is deepest, the processing proceeds to step S16,in which the size of the focusing detection region is set at maximum andit is fixed centrally within the picked-up picture. Note that theposition and size of this focusing detection region may be the same asthose for the initial setting region set at step S1, or may be set inother ways.

If the depth of field is DP2 that is medium, the processing proceeds tostep S17, in which the size and response speed of the focusing detectionregion is set at medium and the moving direction is set to be onlyhorizontal.

If the depth of field is DP1 that is shallowest, the processing proceedsto step S18, in which the size and the response speed of the focusingdetection region are set at minimum and at maximum, respectively, whilethe moving direction of the focusing detection region is set to be bothhorizontal and vertical.

The reason that the size, response speed and moving direction of thefocusing detection region are variably controlled based on the depth offield will be explained in detail with reference to FIG. 4.

As shown in step S18, when the depth of field is DP1, that is,shallowest, the size of the focusing detection region is set minimum, asshown in FIG. 4A, and more specifically, it is set on a regionlongitudinally 30% and transversely 30% for the entire screen. And themoving direction is allowed upward and downward, left and right, anddiagonally.

As shown in step S17, if the depth of field is DP2, that is, medium, thesize of the focusing detection region is set at a medium valuelongitudinally 40% and transversely 30% for the entire screen, as shownin FIG. 4B, with the moving direction being only horizontal, and theresponse speed being set at a medium value.

As shown in step S16, if the depth of field is DP3, that is, deepest,the size of the focusing detection region is set at maximumlongitudinally 60% and transversely 60% for the entire screen, as shownin FIG. 4C, in which the focusing detection region is fixed.

Generally, when the depth of field is shallow, the focusing degreelargely varies between the focusing and unfocusing states in thepicked-up picture, resulting in a state where a main object is easilyfocused on, and can be distinctly distinguished from the background,whereby the high-frequency component from the main object can becorrectly detected, and the changes of the high-frequency component dueto the drift of the focusing point and the movement of the object can bealso precisely detected. Accordingly, as the focusing detection regioncan catch and track the main object correctly, the size thereof is setminimum. And when the depth of field is shallow, the focal distance islong, and the proportion of the object occupying within the picked-uppicture is often large, so that a slight movement thereof appears on thepicked-up picture to an larger extent, thereby the response speed of thefocusing detection region must be set at a higher speed.

When the depth of field is deep, the focusing more easily occurs at morepoints on the picked-up picture, irrespectively of the main object, sothat the position at the peak point of the high-frequency component ofimage can not be fixed due to their frequent changes, which makes itdifficult to perform the normal tracking operation. In other words, insuch a state that the depth of field is so deep as to be likely to focuson an object, the need of tracking the object for the focusing isreduced. When the zoom lens is moved to the wide side to make the depthof field deep, the angle of view becomes wide, so that the movement ofobject is slower generally and less particularly in the verticaldirection. Accordingly, the focusing detection region should be set tobe great to avoid malfunctions owing to the far and near contention, andbe fixed at the central portion within the picked-up picture.

When the depth of field is medium as above shown at step S17, the sizeand the response speed of the focusing detection region are set atmedium and the moving direction of the focusing detection region is madeonly in the horizontal direction where most of the movement occurs,since it is an intermediate state between the deep and shallow cases.

In this way, by controlling finely the size, moving direction andresponse speed of the focusing detection region with the depth ofobject, unnecessary tracking operation is eliminated, so that a smoothertracking can be implemented.

Here, turning to the flowchart of FIG. 2 again, after the settingcondition of the focusing detection region is determined in accordancewith a pick-up situation at steps S16, S17 and S18 as above described,the processing proceeds to step S19, in which based on the horizontaland vertical coordinates of a peak point detected position of thehigh-frequency component within the current field which have been outputfrom the peak position detection circuit 17 and stored in apredetermined memory area within the logic control section 18, and inview of the information about the response speed and moving direction ofthe focusing detection region which have been obtained at steps S16-S18,the move position at the next field of the focusing detection regioncentered on the previously indicated peak position can be operated.

In this case, if the setting position of the focusing detection regionis determined by averaging the information at a predetermined number offields in the past, rather than only by the comparison with theinformation at the previous field, a stabler position setting can beperformed without influence such as noise (for example, a method forsetting the focusing detection region can be applied, as disclosed inJapanese Patent Application No. 1-213921 filed previously by the presentapplicant.)

At step S20, the coordinate values of the focusing detection regionwithin the picked-up picture of the next field obtained at the previousstep are checked to see in which direction they are changed, comparedwith the coordinates within the current picked-up picture, and if it isother than a predetermined moving direction, the region moving directionis set not to be that direction.

As step S21, the size of the focusing detection region is set, based onthe size of the focusing detection region obtained at previous stepsS16-S18.

At step S22, based on the information of the position and size of thefocusing detection region set at the above-mentioned flow, a gate pulseis supplied to the gate circuit 16, in order to control the samplingposition of a pick-up signal within the picked-up picture, or thesetting position of the focusing detection region. Thus, the positionand size of the focusing detection region within the picked-up picturecan be updated.

This gate pulse is also supplied to the display circuit 22 at the sametime, where it is controlled by a control signal from the logic controlcircuit 18. And at step S23, it is converted into a blinking displaysignal, which indicates the display of the focusing detection regionaccording to that mode, or the object tracking mode set at step S4, tosuperimpose it onto the monitor screen 23.

At a stage where the above flow has been executed, one object trackingoperation terminates and returns to step S2.

In this way, it is possible to track a moving object automatically, bydetecting the movement of the peak detection position.

It should be noted that if it is determined at step S14 as abovedescribed that a high precision tracking of an object is impossible dueto a low brightness of the object, as a result that the information ofan object brightness fetched through the object decision filter 13 isobtained, it means that the object does not exist within the focusingdetection region, or it is placed in an extremely unfocused state,whereby the movement of the focusing detection region becomes unstable,or malfunctions may occur, in tracking the object, so that the focusingoperation itself becomes difficult. And so the processing proceeds tostep S24 to forcefully set the position of the focusing detection regionto the reset position, and stop the tracking operation. This resetoperation is performed in such a way that the initial positioncoordinates and the size of the focusing detection position in almostcentral portion within the picked-up picture set at step S1 are set, andthen step S25, a gate pulse corresponding to the reset position isoutput to the gate circuit 16.

After the reset operation of the focusing detection region is performedwhen the object tracking is impossible, the processing proceeds to stepS35, in which the operation transfers to the object tracking stand-bymode, with the focus detection region displayed within the monitorscreen in accordance with that mode, as previously described.

Thus, when the tracking is impossible, malfunctions with the focusingdetection region are thereby avoided, and the movement becomes natural.

By repeating the above control flow with field periods, it is possibleto perform the automatic tracking of a moving object while focusingthereon.

It should be noted that according to the above-mentioned example, whenthe depth of field is at the medium level, the movement direction forthe focusing detection region was made only horizontal, but is notlimited to that, and therefore, taking into consideration that theweighting of movement in the vertical direction becomes small, it may bepermitted to move in both the horizontal and upper directions, in such amanner as shown in FIGS. 5A-5C. The relationship between FIGS. 5A-5C isthe same as that between FIGS. 4A-4C.

In the above-mentioned example, the depth of field is controlled bydividing it into three stages, but the number of stages is not limitedto three, and so it is possible to control, for example, at two or fivestages. In changing the number of stages, however, the size, movementrange and response speed of the focusing detection region must be ofcourse optimized, depending on each depth of field that was divided.

As described above, the pick-up device according to the presentinvention can continue to focus on a moving object reliably, and performthe stable and precise object tracking without malfunctions such as thefar and near contention, because a main object can be always caughtwithin the focusing detection region, irrespectively of the depth offield, by appropriately controlling or switching the size, movingdirection and response speed of the focusing detection region within thepicked-up picture depending on the depth of field.

As described previously, as automatic focusing device which isconstructed to continue to focus on a moving object by the tracking isnot at present provided with a feature that it can notify an operator ofthe information of whether the focusing adjustment is performed inconjunction with the automatic object tracking operation, or it isperformed in the normal fixed focusing detection region, so that theoperator can not know promptly a current operation state.

Accordingly, the operator can not recognize correctly an object that iscurrently focused on, even without a notice that an object other thanthe object to be focused is tracked, so that there is a risk thatvarious malfunctions or misoperations may occur, in cases where thevariations of the object can not be tracked, or the automatic trackingmode is not set when a stopped object starts to move, or conversely, thefocusing detection is considered to be performed with the focusingdetection region fixed, but since the automatic tracking mode has beenset, the focusing detection region might follow previous object inchanging the object to be focused, thus causing the main object not tobe focused correctly.

Even though the detection region is displayed within the monitor screen,a decision is difficult whether or not an object of interest iscorrectly tracked when the screen is confused, and so effective means toraise the accuracy of the object tracking is desired.

Referring now to the flowchart of FIG. 6 and FIG. 7, a second example inaccordance with the present invention will be described to resolve theabove mentioned problems.

This example is constructed to provide the display of a focusing state,in addition to the display of the object tracking state in the firstexample as previously described.

As the circuitry of this example is the same as that shown in FIG. 1,the explanation therefor is omitted. This example is implemented bychanging the control algorithm for the logic control section 18.

An overall control operation for the focusing detection region in anautomatic focusing device according to this example will be describedsequentially with reference to the flowchart shown in FIG. 6.

It should be noted that also in this example, the automatic objecttracking operation is performed on the AF (automatic focusingadjustment) mode, while it is placed in an inoperative state on themanual focusing adjustment mode, where the focusing detection region isnot displayed onto the monitor screen.

There are provided in this example, the AF mode accompanying the objecttracking operation and the normal AF mode not accompanying the objecttracking operation, which can be distinguished from each other duringoperation, with an indication within the monitor screen.

In the same figure, if the object tracking control flow is started, adetermination is made at step 101 whether or not the automatic objecttracking mode is selected with the pick-up mode changeover switch notshown, and if the automatic tracking mode is not selected, theprocessing proceeds to step S127, in which the focusing detection regionis fixed at a predetermined setting position on the central portionwithin the picked-up picture by controlling the gate circuit 16, in thesame way as in the previous example, and the lighting display of thefocus detection region within the monitor screen 23 is set bycontrolling the display circuit 22.

Next, at step 128, an iris value F is read from the iris encoder 21, andat step 129, a focal distance information f is read from the zoomencoder 20, both of which are fetched into the logic control circuit 18and stored in RAM not shown.

At step S130, the depth of field DP is obtained from the information ofthe iris value and focal distance stored in the logic control circuit18, with such a method as will be described later.

At step S131, an unfocused width information is fetched from theunfocused width detection circuit 15, and at step 132, a peak value ofthe high-frequency component within an image signal is fetched from thebandpass filter 14, which are stored in RAM within the logic controldevice 18.

At step S133, the drive direction and the amount of drive for thefocusing lens 1A are obtained, with the focusing detection region fixed,and based on the high-frequency component and the unfocused widthinformation which are output from the bandpass filter 14 and theunfocused width detection circuit 15, respectively, as described above,and at step S134, the focusing lens 1A is actually driven according tothis information.

After terminating the flow of the AF operation, the processing proceedsto step S135, in which the tracking region is displayed within themonitor screen 23, via the display circuit 22, in accordance with thesetting for the lighting display of the tracking (focusing detection)region conducted at step S127. As above described, in the normalautomatic focusing adjustment mode not accompanying the object trackingoperation, the tracking (focusing detection) region is displayed bylighting within the monitor screen.

At step S101, if the automatic object tracking mode has been set withthe pick-up mode changeover switch not shown, the processing proceeds tostep S102, in which the setting for the blinking display of the trackingregion (also used as the focusing detection region) within the monitorscreen is performed, in order to indicate the automatic object trackingmode for continuing to focus on a moving object while automaticallytracking it within the picked-up picture.

Entering the automatic object tracking operation, an iris value from theiris encoder 21 and a focal distance information from the zoom encoder20 are read into the logic control circuit 18 in a field period, atsteps S103 and S104, respectively, and then converted into digital dataof for example one byte, with the A/D converter within the logic controlsection 18, which are stored into RAM not shown.

At step S105, the depth of field DP is obtained based on the iris valueF and focal distance f fetched into the logic control circuit 18 atsteps S103 and S104. This operation for the depth of field is performedwith a decision table for the depth of field as shown in FIG. 3, whichhas been written into ROM within the logic control circuit 18, as in theprevious example.

At step S106, from the output of the peak position detection circuit 17,the information of horizontal and vertical positions for a peak value ofthe high-frequency component of a brightness signal within one fieldperiod, in a block unit within the picked-up picture, is read into thelogic control circuit 18.

At step S107, the analog contrast information within that field outputby the object decision filter 13 is converted into a digital form withthe A/D conversion, which is read into a predetermined memory areawithin the logic control circuit 18, and at step S108, a predeterminedoperation is performed to determine the contrast of object.Specifically, the information of the brightness signal level output bythe object decision filter 13 is compared with a predetermined thresholdto determine the contrast of object, and it is determined whether a highprecision automatic tracking based on the change of peak value of thehigh-frequency component is possible, or the object tracking isimpossible due to a low brightness.

If it is determined at step S108 that the contrast of object is so highthat the object reliably exists within the focusing detection region,and the object tracking with a high precision is possible, theprocessing proceeds to steps S109 and the following, in which the size,moving direction and response speed of the focusing detection region(object tracking region) are obtained, based on the information of thedepth of field DP obtained at step S107.

The processings with the settings of the position, moving direction andsize of the focusing detection region in the steps S109-S116 are thesame as those for steps S15-S22 in the flowchart of FIG. 2 in theprevious example, and so the explanation therefor will be omitted.

Thus, the position and size of the focusing detection region within thepicked-up picture are actually updated.

If the settings of position and size of the focusing detection region(tracking region) at steps S109-S116 have been completed, the processingtransfers to the display process for displaying the state of trackingoperation as shown in steps S117-S120.

That is, in tracking an object automatically, according to thisinvention, an operator can distinguish between a case where the trackingoperation is normally performed by focusing on the object and a casewhere it is not normally performed due to a large deviation out of thefocusing point, with different periods of blinking of display of thefocusing detection region (tracking region) within the monitor screen.

Transferring to step S117, a determination is made whether or not theobject is located near the focusing point.

More specifically, from a characteristic curve representing the relationbetween the focusing lens position and the peak value of high-frequencycomponent or the level of unfocused width information signal changingtherewith, as shown in FIG. 7, it is determined whether it is locatednear the focusing point, whereby the focusing lens 1A is subject to thehill-climbing control in accordance with the characteristic curve whenin a state of being off the focusing point, and is stopped at thefocusing point, while the decision of unfocusing is made for therestart.

Accordingly, in this example, whether or not the object tracking isnormally performed is determined from the focusing state or thecontrolled state of the focusing lens.

More specifically, when the focusing lens is controlled with thehill-climbing, it is decided that the object tracking is not normallyperformed, because the object is not yet focused on, or it does notexist within the tracking region.

On the other hand, when the decision of unfocusing is being made, it isa state where the object is currently focused on, and so the normalobject tracking is decided.

And as a result of such decision, if the object tracking operation isnormally performed, the tracking region blinking period is made fast,while if the object tracking operation is not normally performed, it ismade slow.

Thus, it is possible for an operator to always recognize clearly whetherthe object tracking is normally performed or not, while automaticallytracking an object.

Referring to a flowchart with respect to the above operations, at stepS117 where the unfocusing decision is performed from the focusingcharacteristic curve of FIG. 7, if it is determined that the object islocated near the focusing point, the processing proceeds to step S118,in which the blinking period of displaying the focusing detection region(tracking region) within the monitor screen is set fast, while if it isdetermined that the hill-climbing control is performed due to anextremely unfocused state largely off the focusing degree, theprocessing proceeds to step S119, in which the blinking period of thefocusing detection region (tracking region) is set slow.

After completing the setting of the blinking period for the focusingdetection region, the processing proceeds to step S120, in which thefocusing detection region is displayed within the monitor screen 23, bycontrolling the display circuit 22, based on the information set atprevious steps S110-S112 and the information of the blinking period setat steps S118-S119.

It should be noted that in this example, a decision of whether or notthe tracking is normally performed by focusing on an object is made fromnoting whether or not the focusing lens 1A is controlled with thehill-climbing, or whether the unfocusing decision is performed after thefocusing lens 1A has been stopped. But, it is also possible to changethe display (blinking period) of the focusing detection region (trackingregion), with a method that from the characteristic curve representingthe relation between the output level of high-frequency component orunfocused width information and the focusing degree, as shown in FIG. 7,it is decided that the object is located near the focusing point, ifthat level is above a predetermined level.

With such level decision method, if the level of high-frequencycomponent is only used, that level largely varies with the brightness ofan object, and so it is better to perform the unfocusing decision byusing the unfocused width information which is not largely subject tothe brightness change (the information concerning the width of edgeportion of an object image, and as it is normalized with the value ofbrightness, it is not subject to the effect of brightness change) andpresents a high detection sensitivity only near the focusing point.

At step S121, the unfocused width information within that field outputfrom the unfocused width detection circuit 15, and at step S122, thepeak value information of high-frequency component within that fieldoutput from the bandpass filter 14 are fetched into the logic controlcircuit 18 in a period of field, respectively, and read into RAM notshown after the A/D conversion within the logic control circuit 18. Andat step S123, the focusing detection is performed using the informationof the depth of field, unfocused width and peak value of high-frequencycomponent, which were obtained at steps S105, S121 and S122,respectively, to operate and determine the drive speed which correspondsto the drive direction and focusing degree of the focusing lens 1A. Inthis case, the speed of the focusing lens is corrected in view of thedepth of field DP obtained from the iris value F and the focal distancef.

In determining the depth of field and the drive speed, as describedpreviously, the operation time can be shortened and the programsimplified, by determining them with reference to an information tableas shown in FIG. 3 or an information table not shown for setting thespeed to determine the speed from the focusing degree and the depth offield.

If the operation of the focusing lens drive information has beencompleted, the processing proceeds to step S124, the focusing lens driveinformation (focusing motor drive speed, drive direction, control signalsuch as drive/stop) that was operated at step S123 is supplied to thefocus motor driving circuit 9 to drive the focusing motor 10, therebymoving the focusing lens 1A to the focusing point.

With the above processings, the control flow of the automatic focusingadjustment operation accompanying the object tracking is completed, theprocessing returns to step S101, and thereafter this flow is repeated ina period of once per field.

In this way, the automatic tracking of a moving object can be performedby detecting the movement of the peak detection point, and it ispossible to catch the object correctly at present and track it whilefocusing on the object of interest.

It should be also noted in this example that if it is determined at stepS108 as above described that a high precision tracking of an object isimpossible due to a low brightness of the object, as a result that theinformation of an object brightness fetched through the object decisionfilter 13 is operated, it means that the object does not exist withinthe focusing detection region, or it is placed in such an extremelyunfocused state that the decision of object is difficult, whereby it maynot only cause malfunctions in tracking the object, but the movement ofthe focusing detection region becomes unstable, and the focusingoperation itself becomes difficult. And so the processing proceeds tostep S125 to forcefully set the position of the focusing detectionregion to the reset position in the central portion within the picked-uppicture, and stop the tracking operation. This reset operation isperformed by transferring to step S126 with the setting of the initialposition coordinates and size of initial state in the almost centralportion within the picked-up picture set when starting the tracking atstep S101, and outputting a gate pulse corresponding to the resetposition to the gate circuit 16.

After the reset operation of the focusing detection region when theobject tracking is impossible, the processing proceeds to step S127 totransfer to the normal automatic focusing adjustment mode notaccompanying the object tracking operation, in which the focusingadjustment operation is performed using the fixed focusing detectionregion within the monitor screen. And the lighting display for the fixedfocusing detection region appears within the screen of the monitor 23,and makes it possible for an operator to recognize that the focusingadjustment mode has been switched.

Thus, the above operation can prevent malfunctions of the focusingdetection region and make the movement natural, when the tracking isimpossible, thereby allowing an operator to recognize the currentpick-up situation.

It should be noted that though it is determined in this example whetherthe tracking operation is normal or not depending the focusing controlstate, in this embodiment, it is also possible to determine whether thetracking operation is normal or not from the output of the objectdecision filter 13, as a previous stage for stopping the trackingoperation, and display it. That is, if the output level of the objectdecision filter 13 is high, it is determined that the object tracking isnormally performed because the contrast of picture is sufficientlyobtained, while when it is below a predetermined level, it is determinedthat a probability that the tracking operation is correctly performed islow, whereby the blinking display period for the tracking region ischanged, as previously described. Further, if the output level of theobject decision filter 13 is lowered, the tracking operation itself isstopped as shown in the above-mentioned flowchart.

Such a configuration makes it possible to recognize the pick-up statemore precisely.

By repeating the above control flow with field periods, it is possibleto perform the automatic tracking of a moving object while focusingthereon.

It should be noted that in the above-mentioned example, ON/OFFindication of the object tracking operation relies on the lighting orblinking of the focusing detection region, but is not limited to it, thedisplay with a color, for example, rather than blinking, is alsopossible, while together with the display of the focusing detectionregion, the pick-up mode may be separately displayed within a screen ofelectronic view finder.

Also in this example, in setting the focusing detection region, when thedepth of field is at the medium level, the movement range for thefocusing detection region is set only horizontal, but is not limited toit, and taking into consideration that the weighting of movement in thevertical direction becomes small, it may be permitted to move in boththe horizontal and upper directions, as shown in FIGS. 5A-5C. Note thatthe corresponding relation of each figure is the same as that in FIGS.4A-4C.

The number of stages for switching the depth of object is notrestricted, or it is possible to control it at five or two stages, forexample, in changing the number of stages, however, the size, movementrange and response speed of the focusing detection region must be ofcourse optimized, depending on each depth of field that was divided, inthe same way as the previous example.

According to this example, the region for tracking an object and thefocusing detection region for detecting the focusing state of the objectare constructed to be the same area, but these regions can be provideddifferently so that the object position is tracked with the objecttracking region, where the focusing detection region is set separately,thereby enabling the size of each region to be set individually.

As described above, an automatic focusing device according to thepresent invention can perform a stable and precise tracking of anobject, by setting a first focusing detection mode in which the focusingoperation is performed by fixing the focusing detection region at apredetermined position on the previously described picked-up picture, ora second focusing detection mode in which the focusing operation isperformed while tracking the object with the previously describeddetection region, wherein it can display the previously describedfocusing detection region within a monitor screen, and furtherdistinctly display within the monitor screen in which mode the currentfocusing detection is placed, i.e., the ON/OFF status of the automaticobject tracking operation, as the above-mentioned first and seconddetection modes are configured to have different displays of thefocusing detection region, so that an operator can recognize a currentpick-up state correctly, and thus various malfunctions and misoperationscan be prevented.

Furthermore, an automatic focusing device with the automatic objecttracking feature according to the present invention can distinctlydisplay within a monitor screen a state where the object tracking isnormally performed to continue to focus on a moving object, or a statewhere the object tracking is not performed normally so that the focusingstate can not be obtained on the object to be tracked, as it isconfigured to display whether or not the object tracking operation isnormally performed, with a decision from a condition of the focusingcontrol system, whereby an operator can recognize the current pick-upcondition correctly, and various malfunctions and misoperations can beprevented.

What is claimed is:
 1. A movement correcting apparatus comprising:movement detecting means for detecting a movement of an image in animage screen from an input image signal; shifting means for shifting aread-out area within the image screen for reading a predetermined imagesignal so as to trace a movement of the image, on the basis of an outputof said movement detecting means; and control means for changing ashiftable range in the image screen of said read-out area on the basisof a focal length.
 2. An apparatus according to claim 1, wherein saidcontrol means changes a size of said read-out range according to thefocal length.
 3. The apparatus according to claim 1, wherein saidread-out range is an object tracking area for extracting a predeterminedimage signal component corresponding to a feature of the image.
 4. Theapparatus according to claim 1, wherein said read out range is a focusdetecting area for detecting a focus state of the image.
 5. Theapparatus according to claim 1, wherein said control means limits movingdirection of said read-out range and moving distance in said imagescreen.
 6. A movement correcting method comprising: a movement detectingstep of detecting a movement of an image in an image screen from aninput image signal; a shifting step of shifting a read-out area withinthe image screen for reading a predetermined image signal so as to tracea movement of the image, on the basis of an output signal generated insaid movement detecting step; and a controlling step of changing ashiftable range in the image screen of said read-out area on the basisof a focal length.
 7. The method according to claim 6, wherein saidcontrolling step includes a step of changing a size of said read-outrange according to the focal length.
 8. The method according to claim 6,wherein said read-out range is an object tracking area for extracting apredetermined image signal component corresponding to a feature of theimage.
 9. The method according to claim 6, wherein said read-out rangeis a focus detecting area for detecting a focus state of the image. 10.The method according to claim 6, wherein said control step includes astep of limiting moving direction of said read-out range and movingdistance in said image screen.
 11. An image sensing apparatuscomprising: movement detecting means for detecting a movement of anobject image in an image screen from an image signal; area setting meansfor moving an image read-out area in the image screen for reading apredetermined image signal so as to trace the movement of the objectimage, on the basis of an output of said movement detecting means;control means for changing a movable range in the image screen of saidread-out area on the basis of a focal length; and display means fordisplaying an image in said read-out area.
 12. The apparatus accordingto claim 11, wherein said read-out range is an object tracking area forextracting a predetermined image signal component corresponding to afeature of the image.
 13. The apparatus according to claim 11, whereinsaid read-out range is a focus detecting area for detecting a focusstate of the image.
 14. The apparatus according to claim 11, whereinsaid control means limits moving direction of said read-out range andmoving distance in said image screen.
 15. A movement correctingapparatus comprising: movement detecting means for detecting a movementof an image in an image screen from an input image signal; shiftingmeans for shifting a read-out area within the image screen for reading apredetermined image signal so as to trace a movement of the image, onthe basis of an output of said movement detecting means; and controlmeans for changing a shiftable range in the image screen of saidread-out area on the basis of a zooming magnification.
 16. An apparatusaccording to claim 15, wherein said control means changes a size of saidread-out range according to the focal length.
 17. The apparatusaccording to claim 15, wherein said read out range is an object trackingarea for extracting a predetermined image signal component correspondingto a feature of the image.
 18. The apparatus according to claim 15,wherein said read-out range is a focus detecting area for detecting afocus state of the image.
 19. The apparatus according to claim 15,wherein said control means limits moving direction of said read-outrange and, moving distance in said image screen.
 20. A movementcorrecting method comprising: a movement detecting step of detecting amovement of an image in an image screen from an input image signal; ashifting step of shifting a read-out area within the image screen forreading a predetermined image signal so as to trace a movement of theimage, on the basis of an output signal generated in said movementdetecting step; and a controlling step of changing a shiftable range inthe image screen of said read-out area on the basis of a zoomingmagnification.
 21. The method according to claim 20, wherein saidcontrolling step includes a step of changing a size of said read-outrange according to the focal length.
 22. The method according to claim20, wherein said read-out range is an object tracking area forextracting a predetermined image signal component corresponding to afeature of the image.
 23. The method according to claim 20, wherein saidread-out range is a focus detecting area for detecting a focus state ofthe image.
 24. The method according to claim 20, wherein said controlstep includes a step of limiting moving direction of said read-out rangeand moving a distance in said image screen.